omap_gpmc causes abort in memory_region_del_subregion

Reported by Alexander Graf:

$ wget http://csgraf.de/tmp/beagle-breaks.qcow2
$ ./arm-softmmu/qemu-system-arm -M beaglexm -nographic -drive file=beagle-breaks.qcow2,if=sd,snapshot=on
[system boots]
Loading KIWI VMX Boot-System...
-------------------------------
Creating device nodes with udev
[ 109.465087] device-mapper: uevent: version 1.0.3
[ 109.491973] device-mapper: ioctl: 4.22.0-ioctl (2011-10-19) initialised: <email address hidden>
[ 111.146972] loop: module loaded
[ 132.458923] st: Version 20101219, fixed bufsize 32768, s/g segs 256
qemu-system-arm: /home/pm215/src/qemu/qemu/memory.c:1303: memory_region_del_subregion: Assertion `subregion->parent == mr' failed.
Aborted